/* Copyright � 2002-2011 by Aidant Systems, Inc., and by Jason Smith. */

/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections;

namespace Spring.Collections;

/// <summary>
/// A collection that contains no duplicate elements.
/// </summary>
/// <seealso cref="Spring.Collections.ISet"/>
[Serializable]
public abstract class Set : ISet
{
    /// <summary>
    /// Performs a "union" of the two sets, where all the elements
    /// in both sets are present.
    /// </summary>
    /// <param name="setOne">A collection of elements.</param>
    /// <returns>
    /// A new <see cref="Spring.Collections.ISet"/> containing the union of
    /// this <see cref="Spring.Collections.ISet"/> with the specified
    /// collection. Neither of the input objects is modified by the union.
    /// </returns>
    /// <see cref="Spring.Collections.ISet.Union(ISet)"/>
    public virtual ISet Union(ISet setOne)
    {
        ISet resultSet = (ISet) this.Clone();
        if (setOne != null)
        {
            resultSet.AddAll(setOne);
        }

        return resultSet;
    }

    /// <summary>
    /// Performs a "union" of two sets, where all the elements in both are
    /// present.
    /// </summary>
    /// <remarks>
    /// <p>
    /// That is, the element is included if it is in either
    /// <paramref name="setOne"/> or <paramref name="anotherSet"/>. The return
    /// value is a <b>clone</b> of one of the sets (<paramref name="setOne"/>
    /// if it is not <see langword="null"/>) with elements of the other set
    /// added in. Neither of the input sets is modified by the operation.
    /// </p>
    /// </remarks>
    /// <param name="setOne">A set of elements.</param>
    /// <param name="anotherSet">A set of elements.</param>
    /// <returns>
    /// A set containing the union of the input sets;
    /// <see langword="null"/> if both sets are <see langword="null"/>.
    /// </returns>
    public static ISet Union(ISet setOne, ISet anotherSet)
    {
        if (setOne == null && anotherSet == null)
        {
            return null;
        }
        else if (setOne == null)
        {
            return (ISet) anotherSet.Clone();
        }
        else if (anotherSet == null)
        {
            return (ISet) setOne.Clone();
        }
        else
        {
            return setOne.Union(anotherSet);
        }
    }

    /// <summary>
    /// Performs a "union" of two sets, where all the elements in both are
    /// present.
    /// </summary>
    /// <param name="setOne">A set of elements.</param>
    /// <param name="anotherSet">A set of elements.</param>
    /// <returns>
    /// A set containing the union of the input sets;
    /// <see langword="null"/> if both sets are <see langword="null"/>.
    /// </returns>
    /// <seealso cref="Union(ISet, ISet)"/>
    public static Set operator |(Set setOne, Set anotherSet)
    {
        return (Set) Union(setOne, anotherSet);
    }

    /// <summary>
    /// Performs an "intersection" of the two sets, where only the elements
    /// that are present in both sets remain.
    /// </summary>
    /// <param name="setOne">A set of elements.</param>
    /// <returns>
    /// The intersection of this set with <paramref name="setOne"/>.
    /// </returns>
    /// <see cref="Spring.Collections.ISet.Intersect(ISet)"/>
    public virtual ISet Intersect(ISet setOne)
    {
        ISet resultSet = (ISet) this.Clone();
        if (setOne != null)
        {
            resultSet.RetainAll(setOne);
        }
        else
        {
            resultSet.Clear();
        }

        return resultSet;
    }

    /// <summary>
    /// Performs an "intersection" of the two sets, where only the elements
    /// that are present in both sets remain.
    /// </summary>
    /// <remarks>
    /// <p>
    /// That is, the element is included only if it exists in both
    /// <paramref name="setOne"/> and <paramref name="anotherSet"/>. Neither input
    /// object is modified by the operation. The result object is a
    /// <b>clone</b> of one of the input objects (<paramref name="setOne"/>
    /// if it is not <see langword="null"/>) containing the elements from
    /// the intersect operation.
    /// </p>
    /// </remarks>
    /// <param name="setOne">A set of elements.</param>
    /// <param name="anotherSet">A set of elements.</param>
    /// <returns>
    /// The intersection of the two input sets; <see langword="null"/> if
    /// both sets are <see langword="null"/>.
    /// </returns>
    public static ISet Intersect(ISet setOne, ISet anotherSet)
    {
        if (setOne == null && anotherSet == null)
        {
            return null;
        }
        else if (setOne == null)
        {
            return anotherSet.Intersect(setOne);
        }
        else
        {
            return setOne.Intersect(anotherSet);
        }
    }

    /// <summary>
    /// Performs an "intersection" of the two sets, where only the elements
    /// that are present in both sets remain.
    /// </summary>
    /// <param name="setOne">A set of elements.</param>
    /// <param name="anotherSet">A set of elements.</param>
    /// <returns>
    /// The intersection of the two input sets; <see langword="null"/> if
    /// both sets are <see langword="null"/>.
    /// </returns>
    /// <seealso cref="Intersect(ISet, ISet)"/>
    public static Set operator &(Set setOne, Set anotherSet)
    {
        return (Set) Intersect(setOne, anotherSet);
    }

    /// <summary>
    /// Performs a "minus" of this set from the <paramref name="setOne"/>
    /// set.
    /// </summary>
    /// <param name="setOne">A set of elements.</param>
    /// <returns>
    /// A set containing the elements from this set with the elements in
    /// <paramref name="setOne"/> removed.
    /// </returns>
    /// <seealso cref="Spring.Collections.ISet.Minus(ISet)"/>
    public virtual ISet Minus(ISet setOne)
    {
        ISet resultSet = (ISet) this.Clone();
        if (setOne != null)
        {
            resultSet.RemoveAll(setOne);
        }

        return resultSet;
    }

    /// <summary>
    /// Performs a "minus" of set <paramref name="anotherSet"/> from set
    /// <paramref name="setOne"/>.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This returns a set of all the elements in set
    /// <paramref name="setOne"/>, removing the elements that are also in
    /// set <paramref name="anotherSet"/>. The original sets are not modified
    /// during this operation. The result set is a <b>clone</b> of set
    /// <paramref name="setOne"/> containing the elements from the operation.
    /// </p>
    /// </remarks>
    /// <param name="setOne">A set of elements.</param>
    /// <param name="anotherSet">A set of elements.</param>
    /// <returns>
    /// A set containing
    /// <c><paramref name="setOne"/> - <paramref name="anotherSet"/></c> elements.
    /// <see langword="null"/> if <paramref name="setOne"/> is
    /// <see langword="null"/>.
    /// </returns>
    public static ISet Minus(ISet setOne, ISet anotherSet)
    {
        if (setOne == null)
        {
            return null;
        }
        else
        {
            return setOne.Minus(anotherSet);
        }
    }

    /// <summary>
    /// Performs a "minus" of set <paramref name="anotherSet"/> from set
    /// <paramref name="setOne"/>.
    /// </summary>
    /// <param name="setOne">A set of elements.</param>
    /// <param name="anotherSet">A set of elements.</param>
    /// <returns>
    /// A set containing
    /// <c><paramref name="setOne"/> - <paramref name="anotherSet"/></c> elements.
    /// <see langword="null"/> if <paramref name="setOne"/> is
    /// <see langword="null"/>.
    /// </returns>
    /// <seealso cref="Minus(ISet, ISet)"/>
    public static Set operator -(Set setOne, Set anotherSet)
    {
        return (Set) Minus(setOne, anotherSet);
    }

    /// <summary>
    /// Performs an "exclusive-or" of the two sets, keeping only those
    /// elements that are in one of the sets, but not in both.
    /// </summary>
    /// <param name="setOne">A set of elements.</param>
    /// <returns>
    /// A set containing the result of
    /// <c><paramref name="setOne"/> ^ this</c>.
    /// </returns>
    /// <seealso cref="Spring.Collections.ISet.ExclusiveOr(ISet)"/>
    public virtual ISet ExclusiveOr(ISet setOne)
    {
        ISet resultSet = (ISet) this.Clone();
        foreach (object element in setOne)
        {
            if (resultSet.Contains(element))
            {
                resultSet.Remove(element);
            }
            else
            {
                resultSet.Add(element);
            }
        }

        return resultSet;
    }

    /// <summary>
    /// Performs an "exclusive-or" of the two sets, keeping only those
    /// elements that are in one of the sets, but not in both.
    /// </summary>
    /// <remarks>
    /// <p>
    /// The original sets are not modified during this operation. The
    /// result set is a <b>clone</b> of one of the sets (
    /// <paramref name="setOne"/> if it is not <see langword="null"/>)
    /// containing the elements from the exclusive-or operation.
    /// </p>
    /// </remarks>
    /// <param name="setOne">A set of elements.</param>
    /// <param name="anotherSet">A set of elements.</param>
    /// <returns>
    /// A set containing the result of
    /// <c><paramref name="setOne"/> ^ <paramref name="anotherSet"/></c>.
    /// <see langword="null"/> if both sets are <see langword="null"/>.
    /// </returns>
    public static ISet ExclusiveOr(ISet setOne, ISet anotherSet)
    {
        if (setOne == null && anotherSet == null)
        {
            return null;
        }
        else if (setOne == null)
        {
            return (Set) anotherSet.Clone();
        }
        else if (anotherSet == null)
        {
            return (Set) setOne.Clone();
        }
        else
        {
            return setOne.ExclusiveOr(anotherSet);
        }
    }

    /// <summary>
    /// Performs an "exclusive-or" of the two sets, keeping only those
    /// elements that are in one of the sets, but not in both.
    /// </summary>
    /// <param name="setOne">A set of elements.</param>
    /// <param name="anotherSet">A set of elements.</param>
    /// <returns>
    /// A set containing the result of
    /// <c><paramref name="setOne"/> ^ <paramref name="anotherSet"/></c>.
    /// <see langword="null"/> if both sets are <see langword="null"/>.
    /// </returns>
    /// <seealso cref="ExclusiveOr(ISet, ISet)"/>
    public static Set operator ^(Set setOne, Set anotherSet)
    {
        return (Set) ExclusiveOr(setOne, anotherSet);
    }

    /// <summary>
    /// Adds the specified element to this set if it is not already present.
    /// </summary>
    /// <param name="element">The object to add to the set.</param>
    /// <returns>
    /// <see langword="true"/> is the object was added,
    /// <see langword="true"/> if the object was already present.
    /// </returns>
    public abstract bool Add(object element);

    /// <summary>
    /// Adds all the elements in the specified collection to the set if
    /// they are not already present.
    /// </summary>
    /// <param name="collection">A collection of objects to add to the set.</param>
    /// <returns>
    /// <see langword="true"/> is the set changed as a result of this
    /// operation.
    /// </returns>
    public abstract bool AddAll(ICollection collection);

    /// <summary>
    /// Removes all objects from this set.
    /// </summary>
    public abstract void Clear();

    /// <summary>
    /// Returns <see langword="true"/> if this set contains the specified
    /// element.
    /// </summary>
    /// <param name="element">The element to look for.</param>
    /// <returns>
    /// <see langword="true"/> if this set contains the specified element.
    /// </returns>
    public abstract bool Contains(object element);

    /// <summary>
    /// Returns <see langword="true"/> if the set contains all the
    /// elements in the specified collection.
    /// </summary>
    /// <param name="collection">A collection of objects.</param>
    /// <returns>
    /// <see langword="true"/> if the set contains all the elements in the
    /// specified collection.
    /// </returns>
    public abstract bool ContainsAll(ICollection collection);

    /// <summary>
    /// Returns <see langword="true"/> if this set contains no elements.
    /// </summary>
    public abstract bool IsEmpty { get; }

    /// <summary>
    /// Removes the specified element from the set.
    /// </summary>
    /// <param name="element">The element to be removed.</param>
    /// <returns>
    /// <see langword="true"/> if the set contained the specified element.
    /// </returns>
    public abstract bool Remove(object element);

    /// <summary>
    /// Remove all the specified elements from this set, if they exist in
    /// this set.
    /// </summary>
    /// <param name="collection">A collection of elements to remove.</param>
    /// <returns>
    /// <see langword="true"/> if the set was modified as a result of this
    /// operation.
    /// </returns>
    public abstract bool RemoveAll(ICollection collection);

    /// <summary>
    /// Retains only the elements in this set that are contained in the
    /// specified collection.
    /// </summary>
    /// <param name="collection">
    /// The collection that defines the set of elements to be retained.
    /// </param>
    /// <returns>
    /// <see langword="true"/> if this set changed as a result of this
    /// operation.
    /// </returns>
    public abstract bool RetainAll(ICollection collection);

    /// <summary>
    /// Returns a clone of the <see cref="Spring.Collections.ISet"/>
    /// instance.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This will work for derived <see cref="Spring.Collections.ISet"/>
    /// classes if the derived class implements a constructor that takes no
    /// arguments.
    /// </p>
    /// </remarks>
    /// <returns>A clone of this object.</returns>
    public virtual object Clone()
    {
        Set newSet = (Set) Activator.CreateInstance(this.GetType());
        newSet.AddAll(this);
        return newSet;
    }

    /// <summary>
    /// Copies the elements in the <see cref="Spring.Collections.ISet"/> to
    /// an array.
    /// </summary>
    /// <remarks>
    /// <p>
    /// The type of array needs to be compatible with the objects in the
    /// <see cref="Spring.Collections.ISet"/>, obviously.
    /// </p>
    /// </remarks>
    /// <param name="array">
    /// An array that will be the target of the copy operation.
    /// </param>
    /// <param name="index">
    /// The zero-based index where copying will start.
    /// </param>
    public abstract void CopyTo(Array array, int index);

    /// <summary>
    /// The number of elements currently contained in this collection.
    /// </summary>
    public abstract int Count { get; }

    /// <summary>
    /// Returns <see langword="true"/> if the
    /// <see cref="Spring.Collections.ISet"/> is synchronized across
    /// threads.
    /// </summary>
    /// <remarks>
    /// <p>
    /// Note that enumeration is inherently not thread-safe. Use the
    /// <see cref="SyncRoot"/> to lock the object during enumeration.
    /// </p>
    /// </remarks>
    public abstract bool IsSynchronized { get; }

    /// <summary>
    /// An object that can be used to synchronize this collection to make
    /// it thread-safe.
    /// </summary>
    /// <remarks>
    /// <p>
    /// When implementing this, if your object uses a base object, like an
    /// <see cref="System.Collections.IDictionary"/>, or anything that has
    /// a <c>SyncRoot</c>, return that object instead of "<c>this</c>".
    /// </p>
    /// </remarks>
    /// <value>
    /// An object that can be used to synchronize this collection to make
    /// it thread-safe.
    /// </value>
    public abstract object SyncRoot { get; }

    /// <summary>
    /// Gets an enumerator for the elements in the
    /// <see cref="Spring.Collections.ISet"/>.
    /// </summary>
    /// <returns>
    /// An <see cref="System.Collections.IEnumerator"/> over the elements
    /// in the <see cref="Spring.Collections.ISet"/>.
    /// </returns>
    public abstract IEnumerator GetEnumerator();

    /// <summary>
    /// This method will test the <see cref="Spring.Collections.ISet"/>
    /// against another <see cref="Spring.Collections.ISet"/> for
    /// "equality".
    /// </summary>
    /// <remarks>
    /// <p>
    /// In this case, "equality" means that the two sets contain the same
    /// elements. The "==" and "!=" operators are not overridden by design.
    /// If you wish to check for "equivalent"
    /// <see cref="Spring.Collections.ISet"/> instances, use
    /// <c>Equals()</c>. If you wish to check to see if two references are
    /// actually the same object, use "==" and "!=".
    /// </p>
    /// </remarks>
    /// <param name="obj">
    /// A <see cref="Spring.Collections.ISet"/> object to compare to.
    /// </param>
    /// <returns>
    /// <see langword="true"/> if the two sets contain the same elements.
    /// </returns>
    public override bool Equals(object obj)
    {
        Set theOtherSet = obj as Set;
        if (theOtherSet == null || theOtherSet.Count != Count)
        {
            return false;
        }
        else
        {
            foreach (object element in theOtherSet)
            {
                if (!this.Contains(element))
                {
                    return false;
                }
            }

            return true;
        }
    }

    /// <summary>
    /// Gets the hashcode for the object.
    /// </summary>
    public override int GetHashCode()
    {
        int hashCode = 0, count = 0;
        foreach (object element in this)
        {
            hashCode += element.GetHashCode();
            count++;
        }

        return count + hashCode;
    }
}
